Dr. Stanley I. Greenspan, a psychiatrist who documented the developmental milestones of early childhood and developed the widely used "Floor Time" method for teaching children with autism and other developmental disorders, died April 27 at Suburban Hospital in Bethesda, Md., of complications from a stroke. He was 68.

According to the Interdisciplinary Council on Developmental and Learning Disorders, which offers training in the Floor Time technique, Greenspan was "the world's foremost authority on clinical work with infants and young children with developmental and emotional problems. His work continues to guide parents, professionals and researchers all over the world."

In the Floor Time method, also known as Developmental, Individual-Difference, Relationship-Based therapy, or DIR, the parent or teacher actually gets down on the floor to interact with the child, responding to and encouraging the child's activities rather than attempting to lead him or her in a particular direction.

The approach relies on engagement of the child through one-on-one interactions, customizes programs to the child's interests and needs and places a high value on emotional awareness and relationships. "We believe the primary problem in individuals with autism spectrum disorders is a biological difficulty in connecting emotion to motor actions and later to symbols," Greenspan wrote.

He believed that emotion was key to early language development and that it could be harnessed by interactions with the child at his or her own level. His approach was to let the child do what he or she wanted and then reinforce it. That allows them to feel more and more competent and begin to flourish, said Dr. T. Berry Brazelton, a Harvard University pediatrician who co-wrote "The Irreducible Needs of Children" with Greenspan in 2000.

Using the technique, Greenspan was often able to help children interact with others even when they previously had been totally unresponsive.

The Floor Time method was an outgrowth of Greenspan's earlier studies on the development of children while he was a researcher at the National Institute of Mental Health.

Austrian neurologist Sigmund Freud and Swiss psychologist Jean Piaget had earlier studied the mental development of infants and children and concluded that they go through distinct stages of maturation. Greenspan built on their work and identified additional stages they had not recognized.

His mapping of childhood events is now routinely used by pediatricians to chart the development of children and to ensure they are making normal progress.

Stanley Ira Greenspan was born in New York on June 1, 1941. He had reading and writing difficulties in childhood, and that taught him two things, he said in a 1996 interview: "One, that kids have different learning styles that are real and need to be paid attention to. And two, that people have an enormous capacity to use their strengths to compensate for any areas of vulnerability."

Greenspan graduated from Harvard University in 1962 and received his medical degree from the Yale School of Medicine in 1966. After an internship and residency in psychiatry, he joined the National Institute of Mental Health in 1970, moving on to George Washington University Medical School in 1982.

He wrote or co-wrote a number of books that outlined his work on developmental milestones in children and explained how to perform Floor Time treatments. His work was the subject of "Life's First Feelings," a 1986 PBS special about the emotional development of babies.

Throughout his career, Greenspan maintained a private practice treating children. He was a founder or co-founder of the Interdisciplinary Council on Developmental and Learning Disorders and Zero to Three, an organization promoting healthy development of infants.

Greenspan's first marriage to Helen Hans ended in divorce. He is survived by his second wife, the former Nancy Thorndike; two daughters, Elizabeth Greenspan of Boston and Sarah Greenspan of Silver Spring, Md.; and a son, Jacob, of Washington, D.C.